Fix simple typo: expoed -> exposed

Closes #139

Author: timgates42

README.md

@@ -261,7 +261,7 @@ like this:
 1. Start `wdb.server.py ` running in a container and expose port `1984` to your
    host computer, this will server the debugging web server.
 2. Start debugging in your app container, making sure to set `WDB_SOCKET_SERVER`
-   to the address of the server container, and point it to the expoed port
+   to the address of the server container, and point it to the exposed port
    `19840` on that server.
 3. When a trace is reached, open up `http://<your-docker-hostname>:1984`